The present invention relates to a system for controlling the jaws of a self-centering platform (pallet) which can be moved between base fittings (pallet supports) carried by the loading and unloading station and the working station of a machine tool.
Machine tools are already known which have self-centering pallets in which the automatic control of the jaws is achieved by incorporating a double-acting hydraulic cylinder in the pallets to act on the drive mechanisms which control the movements of the respective jaws. The opposing chambers of the hydraulic cylinder communicate through a pair of supply and discharge ducts with the same number of ducts of a control circuit formed, outside the pallet, in the spindle which supports the latter.
However, in the case of self-centering pallets which can be moved between pallet supports carried by the loading and unloading station and the working station of a machine tool, such as a vertical turning machine, the control for the jaws is manual because of the difficulty of keeping these jaws in the clamping position when the pallet is removed from its support provided with ducts belonging to a hydraulic control circuit outside the pallet.